fix warning about types

This commit was SVN r13992.

ompi/class/ompi_fifo.h

@@ -422,7 +422,7 @@ void *ompi_fifo_read_from_tail(ompi_fifo_t *fifo)
         opal_atomic_lock(&(fifo->fifo_lock));
         if(fifo->tail->cb_overflow == true) {
             fifo->tail->cb_overflow = false;
-            if(fifo->head == ((char*)fifo->tail) + fifo->offset) {
+            if(fifo->head == (ompi_cb_fifo_wrapper_t*) ((char*)fifo->tail) + fifo->offset) {
                 opal_atomic_unlock(&(fifo->fifo_lock));
                 return return_value;
             }